I just went back and took the tour of SE, just like a beginner might.
After a brief (and very good) description, there are two buttons that newbies can use to start to look at the hot questions or the areas. But there is no button to get to learning more about such things as how to sign up as a user, or how to log into an area.
Admittedly, this material is premature for someone who just wants to get a feel for SE before getting involved. But I still think it would be good to provide the button for people who want to go in that direction.
EDIT: I voted to delete this shortly after posting it, but so far it hasn't gone away. I forgot that people don't sign into SE itself, but into one of the areas. If I had remembered that, I would not have posted it.